Automated capillary electrochromatography tandem mass spectrometry using mixed mode reversed-phase ion-exchange chromatography columns

An automated injection system for capillary electrochromatography (CEC), co mbined with a short in-house designed and constructed micro-electrospray CE C mass spectrometry interface, for automated CEC/MS(/MS), electro-osmotic f low (EOF) infusion and how-injection analysis, is coupled to an electrospra y mass spectrometer, The system is used with C-18, C-6 strong cation exchan ge (SCX) and SCX columns, resulting in good reproducibility, sensitivity, s electivity and high efficiencies for small cationic compounds, even with th e use of the SCX columns. Linear calibration lines with good correlation fo r these basic compounds were constructed from high picomolar to low micromo lar range on the C-6/SCX and from low nanomolar to low micromolar on the SC X column. Efficiencies up to 360 000 and 400 000 plates/m are reproducibly obtained for the same charged compounds on the C-6/SCX and SCX column, resp ectively, and detection limits in the high picomolar range on the C-6/SCX a nd in the low nanomolar range on the SCX column are achieved. Application t o the separation of 14 tags (used in code reading in combinatorial chemistr y) on a SCX column is demonstrated. Copyright (C) 1999 John Wiley & Sons, L td.